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EFS CSI Driver

Before diving into this section, you should be familiar with the Kubernetes storage objects (volumes, persistent volumes (PV), persistent volume claims (PVC), dynamic provisioning and ephemeral storage) that were introduced in the Storage main section.

The Amazon Elastic File System Container Storage Interface (CSI) Driver enables you to run stateful containerized applications by providing a CSI interface that allows Kubernetes clusters running on AWS to manage the lifecycle of Amazon EFS file systems.

To utilize Amazon EFS with dynamic provisioning on our EKS cluster, we first need to confirm that we have the EFS CSI Driver installed. The driver implements the CSI specification which allows container orchestrators to manage Amazon EFS file systems throughout their lifecycle.

For improved security and simplified management, you can run the Amazon EFS CSI driver as an Amazon EKS add-on. Since the required IAM role has already been created for us, we can proceed with installing the add-on:

~$aws eks create-addon --cluster-name $EKS_CLUSTER_NAME --addon-name aws-efs-csi-driver \
--service-account-role-arn $EFS_CSI_ADDON_ROLE
~$aws eks wait addon-active --cluster-name $EKS_CLUSTER_NAME --addon-name aws-efs-csi-driver


Let's examine what the add-on has created in our EKS cluster. For example, a DaemonSet that runs a pod on each node in our cluster:


~$kubectl get daemonset efs-csi-node -n kube-system
NAME           DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR                 AGE
efs-csi-node   3         3         3       3            3           kubernetes.io/os=linux        47s


The EFS CSI driver supports both dynamic and static provisioning. For dynamic provisioning, the driver creates an access point for each PersistentVolume, but requires an existing AWS EFS file system that must be specified in the StorageClass parameters. Static provisioning also requires a pre-created AWS EFS file system, which can then be mounted as a volume inside a container using the driver.


An EFS file system has been provisioned for us, along with mount targets and the required security group that includes an inbound rule allowing NFS traffic to the EFS mount points. Let's get its ID which we'll need later:


~$export EFS_ID=$(aws efs describe-file-systems --query "FileSystems[?Name=='$EKS_CLUSTER_NAME-efs-assets'] | [0].FileSystemId" --output text)
~$echo $EFS_ID
fs-061cb5c5ed841a6b0


Next, we'll create a StorageClass object configured to use our pre-provisioned EFS file system and EFS Access points in provisioning mode.


Using Kustomize, we'll create the storage class and inject the EFS_ID environment variable into the filesystemid parameter:


~/environment/eks-workshop/modules/fundamentals/storage/efs/storageclass/efsstorageclass.yaml
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: efs-sc
provisioner: efs.csi.aws.com
parameters:
  provisioningMode: efs-ap
  fileSystemId: ${EFS_ID}
  directoryPerms: "700"



Apply the kustomization:


~$kubectl kustomize ~/environment/eks-workshop/modules/fundamentals/storage/efs/storageclass \
  | envsubst | kubectl apply -f-
storageclass.storage.k8s.io/efs-sc created


Let's examine the StorageClass. Note that it uses the EFS CSI driver as the provisioner and is configured for EFS access point provisioning mode with the file system ID we exported earlier:


~$kubectl get storageclass
NAME            PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
efs-sc          efs.csi.aws.com         Delete          Immediate              false                  8m29s
~$kubectl describe sc efs-sc
Name:            efs-sc
IsDefaultClass:  No
Annotations:     kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{},"name":"efs-sc"},"parameters":{"directoryPerms":"700","fileSystemId":"fs-061cb5c5ed841a6b0","provisioningMode":"efs-ap"},"provisioner":"efs.csi.aws.com"}
 
Provisioner:           efs.csi.aws.com
Parameters:            directoryPerms=700,fileSystemId=fs-061cb5c5ed841a6b0,provisioningMode=efs-ap
AllowVolumeExpansion:  <unset>
MountOptions:          <none>
ReclaimPolicy:         Delete
VolumeBindingMode:     Immediate
Events:                <none>


Now that we understand EKS StorageClass and the EFS CSI driver, we'll proceed to modify the assets microservice to use the EFS StorageClass with Kubernetes dynamic volume provisioning and a PersistentVolume for storing product images.